In automobile factories, windows are installed using robots and computer controlled processing which facilitates the use of a variety of high performance adhesives, for instance, nonconductive adhesives and high modulus adhesives. These adhesives have to be storage stable and be readily applied under high shear, for example, to a windshield, while retaining the bead shape so that the windshield can be properly fitted to the automobile. This typically has been achieved by one part moisture curable polyurethane prepolymer based adhesives having fillers, with the prepolymers having sufficient molecular weight, so that they are still pumpable and can be applied to the windshield without sagging or stringing in the time it takes to place the windshield on the automobile. These adhesives contain free isocyanate groups that are regulated and will be subject to more stringent regulation.
Silane modified polymers (SMPs) have been used to replace the moisture curable polyurethane based adhesives. SMPs generally are comprised of flexible polymeric backbones that are terminated by moisture reactive (hydrolysable) silane terminal groups. SMPs, generally, have been made by three routes. The first, illustrated by U.S. Pat. No. 3,971,751, involves hydrosilylating a silicon hydride having hydrolysable silyl groups with an allyl terminated polyether, where the allyl terminated polyether was formed from a polyether polyol. Unfortunately, these SMPs tend to be expensive due to the cost to fabricate the allyl terminated polyether due to the use of chlorine and alkali that must be removed and disposed. The second, illustrated by U.S. Pat. No. 3,632,557, generally involves reacting an aminosilane with an isocyanate terminated prepolymer resulting in trialkoxysilyl end groups with polyether polymer backbones containing urea linkages. Adhesives with these prepolymers tend to have high viscosities and low elongation. The third, illustrated by U.S. Pat. Nos. 4,625,012 and 6,355,127 involves reacting an isocyanato organosilane with a polyurethane having terminal active hydrogens. Likewise, these have suffered from high viscosities and low elongations.
Recently, PCT Appl. Nos. WO2012/003212, WO2012/003216, and WO2012/003187 have described hydrosilylating a silicon hydride having hydrolysable silyl groups with an allyl terminated polyether, where the polyether has only one allyl terminal group and the other terminal group is an alcohol. After hydrosilylation, the terminal alcohol is reacted with a diisocyanate resulting in urethane linkage and isocyanate terminal group. This is then reacted with a polyether polyol to form SMPs.
Each of the above have suffered from complex and expensive processes to make a moisture curable SMP useful for an adhesive composition.
What is needed is a SMP composition that is useful as an adhesive for bonding glass into a structure avoiding some of shortcomings they have exhibited such as those described above.